In the past, many adjustable stairs have been devised. Several of these involve complex metal steps with pairs of stringers on both sides of the steps, one stringer of each pair being movable with respect to the other stringer so as to position the steps in horizontal positions in the stairwell. Usually, in such an arrangement, both stringers on both sides of the stair are secured flat against the opposed wall to retain the steps in horizontal positions. The patent to J. I. Whitehead U.S. Pat. No. 3,470,664 is an example of such a structure.